Multiple cystic and focal encephalomalacia in infancy and childhood with brain stem damage.

Two cases are described in which damage to the brain stem was associated with extensive necrosis of the cerebral hemisphere. In the first case--a monochorionic twin--there was clear evidence that injury of an ischaemic or hypoxic type had occurred during fetal life and some evidence that an inadequate share of the placental circulation was an important aetiological factor. In the second case death occurred 4 yr after an asphyxial episode at birth. The lesions in the hemispheres and brain stem were extensive, although less than in the first example. The lesions are discussed in the context of our knowledge of the anatomy and physiology of the developing nervous system. Although they cannot as yet be fitted into the concepts of "critical periods" and "vulnerable periods" of development, this is perhaps because observations on human cases are scanty in comparison with the extensive animal studies which have been reported. The lesions are contrasted and compared with those seen in animals.